The acoustic wave device is a device having an inter-digital transducer (IDT) formed on a piezoelectric substrate such as lithium tantalate (LiTaO3:LT) substrate or lithium niobate (LiNbO3:LN) substrate. The LT and LN have high thermal expansion coefficients that are six times higher than the thermal expansion coefficient of silicon (the thermal expansion coefficients of LT and LN are about 16×10−6/K and 15×10−6/K, respectively, while the thermal expansion coefficient of silicon is about 2.6×10−6/K). Then, if the LT or LN substrate is used in the acoustic wave device, there arises a significant problem of change in filtering performance due to temperature change. Therefore, temperature compensation is performed in various methods.
For example, the patent document 1 discloses a technique of bonding a thinned piezoelectric substrate and an amorphous piezoelectric substrate for temperature compensation directly or via an inorganic thin layer. Besides, the patent document 2 discloses bonding an insulating substrate for temperature compensation and an IDT-formed and then thinned piezoelectric substrate with use of an adhesive member made of glass material.    [Patent document 1] Japanese Patent Application Laid-Open No. H6-326553    [Patent document 2] Japanese Patent Application Laid-Open No. 2002-16468